JP2006241333A - Heat conductive composition and heat conductive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat conductive composition for efficiently transferring the heat generated from a heat generator part of CPU, MPU and the like to a heat dissipation part of a heat sink, a heat pipe and the like, particularly a heat conductive composition and a heat conductive sheet excellent in shape follow-up properties, flexibility, and adhesion properties capable of coping with a sudden rise in the temperature of the heat generator part and excellent in handling properties and recycling properties. <P>SOLUTION: The heat conductive composition 100 comprising 50-95 pts.wt. side chain crystallizable polymer A which softens at the heat generation temperature of CPU 4, 50-5 pts.wt. side chain crystallizable polymer B which is incompatible with the side chain crystallizable polymer A and exhibits flowability at the heat generation temperature of CPU 4, and furthermore 10-300 pts.wt. heat conductive filler 2 based on 100 pts.wt. solid content of a mixed polymer 1 of the side chain crystallizable polymer A and the side chain crystallizable polymer B and the heat conductive sheet are placed in between CPU 4 and a heat sink 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermally conductive composition and a thermally conductive sheet for efficiently transferring heat generated from a heating element such as a CPU or MPU to a heat radiating component such as a heat sink or a heat pipe.

  Semiconductor parts such as CPUs and MPUs are used as heating element parts that generate heat in electronic products such as notebook personal computers and desktop personal computers. In recent years, these semiconductor components have been increased in frequency with higher performance, and accordingly, power consumption and heat generation tend to increase. Further, in such a semiconductor component, malfunction due to heat and deterioration in performance are likely to occur in proportion to an increase in the amount of heat generated. For this reason, it has been common to install heat-dissipating parts such as heat sinks and seat pipes on these heating elements to suppress temperature rise of the heating elements by air cooling method or water cooling method to suppress malfunctions and performance degradation. Has been done. However, since the surface of the heating element is often not smooth, a heat conductive adhesive sheet having flexibility is interposed to improve the adhesion between the heating element and the heat dissipation component, The contact was secured and the heat dissipation effect was improved.

As the adhesive sheet, there is known a heat conductive adhesive sheet obtained by adding a compound such as a higher fatty acid incompatible with the adhesive and heat conductive fine particles to an adhesive mainly composed of an acrylate ester. Such a heat conductive adhesive sheet receives heat from a heating element, so that the compound reaches a temperature higher than the melting point and melts, and has an appropriate flexibility and shape followability as an adhesive sheet, thereby providing a heat dissipation effect. (For example, refer to Patent Document 1).
JP 2003-105299 A (page 1)

  However, since the adhesive sheet described in Patent Document 1 is insufficiently flexible in a state where the main component adhesive is heated, it is difficult to completely adhere the heating element and the heat dissipation component. there were. Further, the temperature of the heating element does not gradually increase, but rapidly increases and decreases depending on the amount of calculation processing of the heating element (CPU). For this reason, it has been important to transmit the heat that rises instantaneously to the heat radiating component to efficiently lower the temperature. From this point, even if the adhesive sheet is interposed between the heat generating element and the heat radiating component, it cannot follow a minute change of the surface of the heat generating element due to a sudden temperature rise, and a high heat radiating effect cannot be obtained.

  In addition, since the adhesive sheet has tackiness at room temperature, the adhesive sheets stick to each other when pasted to the heating element, and thus there is a problem in workability and handleability when reattaching to the heating element.

  Also, when considering recycling of CPU, heat sink, etc., the adhesive sheet has a small decrease in adhesive force even during heat generation, so it is not possible to easily separate the heat radiating parts from the heating element, and forcibly removing it, A part of the adhesive remains on the surface of the heating element or the heat radiating member, so-called adhesive residue is generated, and the recyclability is poor.

  The present invention has been made to solve the above-mentioned problems, and is a heat conductive composition for efficiently transferring heat generated from a heat generating component such as a CPU or MPU to a heat radiating component such as a heat sink or a heat pipe. The thermal conductive composition and the thermal conductivity are excellent in shape followability and adhesiveness that can cope with a rapid temperature rise of the CPU, and are excellent in handleability and recyclability. The purpose is to provide a sheet.

  In order to achieve the above object, the heat conductive composition and the heat conductive sheet of the present invention are as follows.

  50 to 95 parts by weight of a first side chain crystallizable polymer that softens at an exothermic temperature of the heating element, and is incompatible with the first side chain crystallizable polymer and exhibits fluidity at the exothermic temperature of the heating element. 50 to 5 parts by weight of a two-side chain crystallizable polymer, and thermal conductivity with respect to 100 parts by weight of the solid content of the mixed polymer of the first side-chain crystallizable polymer and the second side-chain crystallizable polymer It contains 10 to 300 parts by weight of a filler.

  The melting points of the first side chain crystallizable polymer and the second side chain crystallizable polymer are both 30 ° C. or higher and crystallize at a temperature lower than the melting point.

  Further, both the first side chain crystallizable polymer and the second side chain crystallizable polymer are 30 to 100 parts by weight of acrylic acid ester or methacrylic acid ester having a linear alkyl group having 16 or more carbon atoms. And a polymer obtained by polymerizing 70 to 0 parts by weight of an acrylic acid ester or methacrylic acid ester having 1 to 12 carbon atoms and 0 to 10 parts by weight of a polar monomer.

  By interposing the heat conductive composition or the heat conductive sheet of the present invention between the heat generator and the heat radiating component, the heat conductive composition is softened and fluidized at the heat generation temperature of the heat generator to increase flexibility. The adhesion between the heating element and the heat dissipation component is improved, and the heat of the heating element can be transmitted to the heat dissipation component well and radiated. In particular, even when the temperature of the heating element is suddenly increased, the shape of the heat conductive composition changes following the change in the surface shape of the heating element, so that the adhesion between the members is maintained, and the heating element is excellent. Heat can be transferred to heat dissipation components. Moreover, since the said heat conductive composition has almost no adhesiveness at room temperature, it is easy to stick or re-apply to a heat generating body.

  For the same reason, the heat dissipating component can be easily separated from the heating element, and the recyclability can be improved. Furthermore, at that time, the thermal conductive composition can be easily peeled off without any adhesive residue on the surface of each member, so that the burden on the subsequent process in recycling is small.

  Hereinafter, embodiments of the present invention will be described.

  First, an embodiment of the thermally conductive composition of the present invention will be described with reference to FIG. The thermally conductive composition 100 of the present invention is incompatible with the side chain crystallizable polymer A in the side chain crystallizable polymer A that is softened at the heat generation temperature of the heat generator, and at the heat generation temperature of the heat generator. This is a composition comprising the mixed polymer 1 to which the side-chain crystallizable polymer B exhibiting fluidity is added, and further the thermally conductive filler 2 added.

  In the present invention, the side chain crystallizable polymers A and B react with temperature changes in a crystalline state, a softened state (in the case of the side chain crystallizable polymer A), and a fluidized state (of the side chain crystallizable polymer B). A polymer that can reversibly undergo phase transition. With respect to this phase transition property, since both polymers are side chain crystallizable polymers, it is possible to quickly react to a temperature change and to undergo phase transition. Therefore, the thermal conductive composition 100 reacts instantaneously to a sudden temperature change, the side chain crystallizable polymer A softens, and the side chain crystallizable polymer B fluidizes, It becomes possible to show flexibility.

  As described above, a heating element such as a CPU generates heat instantaneously and increases in temperature depending on the amount of use. At that time, by interposing the heat conductive composition 100 of the embodiment between the heat generating element and the heat radiating component, the heat conductive composition 100 against a minute change of the surface of the heat generating element due to a rapid temperature change. Can quickly follow and change and can adhere to the surface of the heating element without any gaps. As described above, the heat resistance is reduced by improving the adhesion, and the heat conductive composition 100 can efficiently transmit the heat from the heating element to the heat radiating component and perform the heat radiation.

  In the thermally conductive composition 100, the ratio of the side chain crystallizable polymers A and B is 50 to 95 parts by weight of the side chain crystallizable polymer A and 50 to 5% by weight of the side chain crystallizable polymer B. Part. Since there are many side chain crystallizable polymers A having a softening property as a proportion, the incompatible side chain crystallizable polymer B was uniformly dispersed in the side chain crystallizable polymer A as a base material. It has a so-called sea-island structure. When the value by weight is in a ratio other than the above, the balance of the sea-island structure in the side-chain crystallizable polymers A and B is lost, and the function as the heat conductive composition 100 is lowered.

  In particular, when the proportion of the side chain crystallizable polymer B having flow characteristics is larger than the above proportion, the island portion of the sea-island structure becomes a continuous shape, and the side chain crystallizable polymer A is side chain crystallized. Possible polymer B is in a state where it cannot be uniformly dispersed. In such a dispersed state, the heat conductive composition 100 is in a brittle state without viscosity at room temperature, and even if it can be formed into a sheet, it is easily broken and difficult to handle. Further, at the heat generation temperature, fluidization of the side chain crystallizable polymer B becomes dominant in the heat conductive composition 100, and the heat conductive composition 100 may flow down from between the heat generator and the heat dissipation component. Is expensive.

  Further, since the side chain crystallizable polymers A and B are incompatible with each other, the softening characteristics of the side chain crystallizable polymer A and the flow characteristics of the side chain crystallizable polymer B interfere with each other. Can be expressed without From this, the heat conductive composition 100 exhibits sufficient flexibility at the heat generation temperature of the heat generator, and can also improve the wettability of the surface by fluidization.

  Therefore, by interposing the thermal conductive composition 100 of the embodiment between the heat generating element and the heat radiating component, the adhesion between the heat generating element and the heat radiating component is improved, and the heat conductive composition 100 is formed without a gap. By closely contacting these surfaces and increasing the pseudo contact area between the members, a high heat dissipation effect can be obtained.

  The side chain crystallizable polymers A and B used in the heat conductive composition 100 are preferably polymers that have a melting point of 30 ° C. or higher and crystallize at a temperature lower than the melting point, for example. Thus, the thermally conductive composition 100 is non-adhesive (or slightly adhesive) at room temperature, so that it is easy to handle and work when re-attaching to a heating element. In addition, the heat radiating component can be easily separated from the heating element at room temperature, and in the separation, the phenomenon of adhesive residue on each member does not occur and the recyclability is excellent.

  Further, since the phase transition characteristic of the heat conductive composition 100 is a reversible chemical characteristic with the melting point of the side chain crystallizable polymers A and B as a boundary, the thermal conductivity is separated after the separation of each member. The composition 100 can be used again and again.

  The side-chain crystallizable polymers A and B each have 30 to 100 parts by weight of an acrylic ester or methacrylic ester having a linear alkyl group having 16 or more carbon atoms and an alkyl group having 1 to 12 carbon atoms. It is preferable that it is a polymer obtained by polymerizing 70 to 0 parts by weight of acrylic acid ester or methacrylic acid ester and 0 to 10 parts by weight of a polar monomer.

  Examples of the acrylic acid ester and / or methacrylic acid ester (hereinafter referred to as (meth) acrylate) having a linear alkyl group having 16 or more carbon atoms include stearyl (meth) acrylate, eicosyl (meth) acrylate, and behenyl (meta). ) A (meth) acrylate having a linear alkyl group having 18 to 22 carbon atoms such as acrylate is preferably used.

  Examples of the (meth) acrylate having an alkyl group having 1 to 12 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate, and lauryl (meth) acrylate. Etc.

  Examples of the polar monomer include carboxyl group-containing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl Ethylenically unsaturated monomers having a hydroxyl group such as (meth) acrylate and 2-hydroxyhexyl (meth) acrylate are used, among which acrylic acid is particularly preferable.

  The weight average molecular weight of the side chain crystallizable polymer A is preferably 10,000 to 300,000. When the weight average molecular weight of the side chain crystallizable polymer A is less than 10,000, the cohesive force of the heat conductive composition 100 is insufficient, the shape of the sheet cannot be maintained, and the handleability is poor. On the other hand, when the weight average molecular weight of the side chain crystallizable polymer A is larger than 300,000, the composition becomes hard and inferior in flexibility, so that the adhesion to the heating element and the heat radiating component is lowered and the heat radiation effect is lowered.

  The weight average molecular weight of the side chain crystallizable polymer B is preferably 1000 to 10,000. If the weight average molecular weight of the side chain crystallizable polymer B is less than 1000, the dispersibility with respect to the side chain crystallizable polymer A is lowered, and the island portions of the sea-island structure are in a continuous form, and heat is generated. Variations in fluidity will occur. Moreover, since fluidity | liquidity will fall when the said weight average molecular weight is larger than 10,000, there exists a possibility that the adhesiveness of a heat generating body and a thermal radiation component may be inferior.

Further, the thermal conductive composition 100 of the present invention has a storage elastic modulus at a temperature of 23 ° C. in the range of 1.0 × 10 ⁶ Pa to 1.0 × 10 ⁸ Pa, and the temperatures of 23 ° C. and 80 ° C. The ratio of storage elastic modulus at ° C. (storage elastic modulus at 23 ° C. ÷ storage elastic modulus at 80 ° C.) is 100 or more, preferably 200 or more. The large value of the ratio of the storage elastic modulus greatly increases the flexibility of the thermal conductive composition 100 at a high temperature (for example, a temperature of 80 ° C.) as compared with a room temperature (for example, a temperature of 23 ° C.). Means. When the value of the storage elastic modulus at the temperature of 23 ° C. or the value of the ratio of the storage elastic modulus at the temperature of 23 ° C. and 80 ° C. is other than the above, the workability at room temperature of the thermally conductive composition 100 and the heat generation temperature There is a risk that the balance with the flexibility will be worse.

  In order to improve thermal conductivity, the thermally conductive filler 2 is added to the thermally conductive composition 100 of the present invention. The heat conductive filler 2 is not particularly limited, and examples thereof include boron nitride, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, and graphite. Further, the shape is not particularly limited, but fine particles having an average particle diameter of 1 to 50 μm are preferable.

  The thermally conductive filler 2 is preferably blended in a proportion of 10 to 300 parts by weight with respect to 100 parts by weight of the solid content of the mixed polymer 1 of the side chain crystallizable polymers A and B. Thereby, when the said heat conductive composition 100 closely_contact | adheres to a heat generating body or a heat radiating component at the heat_generation | fever temperature, heat can be favorably transmitted from a heat generating body to a heat radiator. When the blending amount of the heat conductive filler 2 is less than 10 parts by weight, the heat conductive composition 100 can maintain flexibility, but heat conductivity is insufficient. Moreover, when the said compounding quantity is higher than 300 weight part, the rigidity of the said heat conductive composition 100 will become high, and since a softness | flexibility falls, the adhesiveness to each member will fall and the heat dissipation effect will reduce.

  In addition, the thermal conductive composition 100 of the present invention may be appropriately added with a crosslinking agent, an anti-aging agent, a plasticizer, a filler, etc. within a range that does not impair flexibility in order to increase heat resistance and cohesion. Also good.

  Moreover, it is preferable that the usage form of the said heat conductive composition 100 of this invention is a sheet form form on handleability. By being in the form of a sheet, it is easy to attach to the surface of the heating element, and it becomes easy to handle. In particular, in the case of a sheet shape, handling properties can be improved by providing release films on both surfaces of the thermally conductive composition 100.

  The thermal conductive sheet may have a thickness of 20 to 200 μm. When the thickness of the heat conductive sheet is less than 20 μm, when the flexibility of the sheet increases due to the heat of the heating element, it becomes difficult to follow the surface shape of the heating element and the heat dissipation component due to insufficient sheet volume. . If the thickness of the sheet is greater than 200 μm, the heat of the heating element may not be efficiently transmitted to the heat radiating component.

  Further, as another embodiment of the present invention, a heat conductive sheet 200 in which the heat conductive composition 100 is provided on both surfaces of a base film 3 having heat conductivity as shown in FIG. 2 may be used. . By adopting a structure in which the base film 3 having thermal conductivity is sandwiched between the thermal conductive compositions 100, the rigidity as the thermal conductive sheet 200 is increased without lowering thermal conductivity, and handling properties are improved. To do. Although it does not restrict | limit especially as said base film 3 which has electroconductivity, For example, what added the heat conductive filler in resin films, such as PET and PE, and metals, such as copper and aluminum Examples thereof include films, metal meshes, metal fiber woven fabrics, and graphite sheets.

  The thickness of each of the thermally conductive compositions 100 provided on both surfaces of the base film 3 is preferably 20 to 100 μm in order to develop shape followability. Moreover, you may affix a release film on both surfaces of this heat conductive sheet 200. FIG.

  Next, an embodiment of a method for using the thermally conductive composition 100 of the present invention will be described with reference to FIG. The above-described heat conductive composition 100 is used in a form interposed between the CPU 4 and the heat sink 5, and the heat sink 5 is fixed to the CPU 4 with a bolt or the like.

  Since the thermally conductive composition 100 is non-adhesive at room temperature, it has an advantage that it can be easily reattached to the CPU 4 and the position of the heat sink 5 can be easily corrected.

  Through this thermally conductive composition 100, the CPU 4 and the heat sink 5 can maintain a close contact state. When the CPU 4 generates heat in this state, when the surface temperature of the CPU 4 reaches the melting point of the heat conductive composition 100, the heat conductive composition 100 immediately undergoes phase transition, softens, and flows, and the fine irregularities on the surface of the CPU 4 By changing following the shape change, the heat of the CPU 4 can be transferred to the heat sink 5 well. Accordingly, it is possible to prevent malfunction of the CPU 4 and deterioration of performance due to heat generation.

  On the other hand, when the usage amount of the CPU 4 is reduced and heat generation is reduced, and the surface temperature of the CPU 4 becomes lower than the melting point of the heat conductive composition 100, the heat conductive composition 100 is crystallized and loses adhesiveness.

  The thermal conductive composition 100 can quickly repeat the crystallization state below the melting point and the softening and fluidization state above the melting point by a chemical phase transition using temperature as a trigger. Thus, the heat generated by the CPU 4 can be efficiently transmitted to the heat sink 5, and as a result, malfunction of the CPU 4 and deterioration of performance can be prevented.

  Further, as described above, the thermal conductive composition 100 loses its adhesiveness at a temperature lower than the melting point. In this state, the heat sink 5 can be easily detached from the CPU 4. Further, when removing, no adhesive residue is generated on the heat sink 5 or the CPU 4 and the recyclability is excellent. Moreover, this heat conductive composition 100 can be repeatedly used from the above-mentioned chemical phase transition characteristic.

  Hereinafter, the thermal conductive composition 100 and the thermal conductive sheet of the present invention will be described in detail with reference to synthesis examples and examples.

  First, a synthesis example of the side chain crystallizable polymer A is shown below.

(Synthesis Example 1)
45 parts by weight of behenyl acrylate, 50 parts by weight of methyl acrylate, 5 parts by weight of acrylic acid, 1 part by weight of perbutyl ND (manufactured by NOF Corporation) as a polymerization initiator, and 230 parts by weight of ethyl acetate / n-heptane (70/30) As a solvent, these monomers were polymerized by stirring at 60 ° C. for 5 hours. The obtained polymer had a weight average molecular weight of 150,000 and a melting point of 57 ° C.

  Here, the melting point will be described. As used herein, “melting point” refers to the temperature at which a particular portion of the polymer that was initially aligned in an ordered arrangement becomes disordered by some equilibrium process. In actual measurement, the prepared side chain crystallizable polymer A is a value measured by a differential thermal scanning calorimeter (DSC) under a temperature rising condition of 10 ° C./min. The same measurement was performed in the following synthesis examples.

(Synthesis Example 2)
A polymer was obtained in the same manner as in Synthesis Example 1 except that 50 parts by weight of butyl acrylate was used instead of 50 parts by weight of methyl acrylate. The obtained polymer had a weight average molecular weight of 150,000 and a melting point of 45 ° C.

(Synthesis Example 3)
A polymer was polymerized under the same conditions as in Synthesis Example 1 using 95 parts by weight of behenyl acrylate, 5 parts by weight of acrylic acid, 1 part by weight of perbutyl ND as a polymerization initiator, and 150 parts by weight of n-heptane as a solvent. The weight average molecular weight of the obtained polymer was 100,000, and the melting point was 70 ° C.
Next, a synthesis example of the side chain crystallizable polymer B is shown below.

(Synthesis Example 4)
Stearyl acrylate 95 parts by weight, acrylic acid 5 parts by weight, dodecyl mercaptan 5 parts by weight, perhexyl PV (manufactured by Nippon Oil & Fats) 1 part by weight with toluene 100 parts by weight as a solvent at 80 ° C. for 5 hours to polymerize these monomers I let you. The weight average molecular weight of the obtained polymer was 7000, and the melting point was 50 ° C.

(Synthesis Example 5)
A polymer was obtained in the same manner as in Synthesis Example 4 except that 95 parts by weight of behenyl acrylate was used instead of 95 parts by weight of stearyl acrylate. The obtained polymer had a weight average molecular weight of 8,000 and a melting point of 70 ° C.

(Synthesis Example 6)
These monomers were polymerized by stirring 95 parts by weight of stearyl acrylate, 5 parts by weight of acrylic acid and 1 part by weight of perhexyl PV (manufactured by NOF Corporation) at 80 ° C. for 5 hours using 100 parts by weight of toluene as a solvent. The weight average molecular weight of the obtained polymer was 30,000, and the melting point was 50 ° C.

  Next, synthesis examples as polymers not corresponding to the side chain crystallizable polymers A and B will be given below.

(Synthesis Example 7)
The mixture was stirred at 60 ° C. for 5 hours with 92 parts by weight of 2-ethylhexyl acrylate, 8 parts by weight of 2-hydroxyethyl acrylate, 1 part by weight of perbutyl ND as a polymerization initiator and 230 parts by weight of ethyl acetate / n-heptane (70/30) as a solvent. These monomers were polymerized. The weight average molecular weight of the obtained polymer was 150,000. The melting point was measured but did not show a clear melting point.

次に、実施例として熱伝導性シートの調整の例を示す。 The physical properties of Synthesis Examples 1 to 7 are listed in Table 1.

Next, the example of adjustment of a heat conductive sheet is shown as an Example.

Example 1
After 90 parts by weight of the polymer of Synthesis Example 1 and 10 parts by weight of the polymer of Synthesis Example 4 were mixed to prepare the mixed polymer 1, nitriding was performed as the heat conductive filler 2 with respect to 100 parts by weight of the solid content of the mixed polymer 1. A thermally conductive composition 100 was prepared by adding 50 parts by weight of boron powder and uniformly dispersing the powder. The heat conductive composition 100 was applied on a PET release film at a thickness of 50 μm to obtain a heat conductive sheet.

(Example 2)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 1 and 10 parts by weight of the polymer of Synthesis Example 5 were mixed to prepare the mixed polymer 1.

(Example 3)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 2 and 10 parts by weight of the polymer of Synthesis Example 4 were mixed to prepare the mixed polymer 1.

Example 4
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 2 and 10 parts by weight of the polymer of Synthesis Example 5 were mixed to prepare the mixed polymer 1.

(Example 5)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 3 and 10 parts by weight of the polymer of Synthesis Example 4 were mixed to prepare the mixed polymer 1.

(Example 6)
A thermally conductive and thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 3 and 10 parts by weight of the polymer of Synthesis Example 5 were mixed to prepare the mixed polymer 1.

(Comparative Example 1)
Preparation of a thermally conductive sheet was attempted in the same manner as in Example 1 except that 40 parts by weight of the polymer of Synthesis Example 1 and 60 parts by weight of the polymer of Synthesis Example 4 were mixed to prepare a mixed polymer. However, the sheet was not viscous and fragile in a raged state, and a sufficient sheet could not be produced.

(Comparative Example 2)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 1 and 10 parts by weight of the polymer of Synthesis Example 6 were mixed to prepare a mixed polymer.

(Comparative Example 3)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 2 and 10 parts by weight of the polymer of Synthesis Example 6 were mixed to prepare a mixed polymer.

(Comparative Example 4)
A thermally conductive sheet was obtained in the same manner as in Example 1 except that 90 parts by weight of the polymer of Synthesis Example 3 and 10 parts by weight of the polymer of Synthesis Example 6 were mixed to prepare a mixed polymer.

(Comparative Example 5)
A heat conductive composition was prepared by uniformly dispersing 50 parts by weight of boron nitride powder as a heat conductive filler with respect to 100 parts by weight of the solid content of the polymer of Synthesis Example 7. Thereafter, a thermally conductive sheet was obtained in the same manner as in Example 1.

(Performance evaluation as a thermal conductive sheet)
(Evaluation-1: Measurement of thermal resistance)
The thermal resistance of the heat conductive sheets prepared in Examples 1 to 6 and Comparative Examples 2 to 5 was measured by the method described below. The release film of the heat conductive sheet was peeled off and sandwiched between a heater member assuming a heating element and a heat dissipation component, and 5 W of power was applied to the heater for 1 minute. Immediately after that, the temperature difference (ΔT) between the surface of the heater member and the surface of the heat dissipating component was measured, and the thermal resistance (° C./W) was determined from the following equation from the numerical value of the obtained temperature difference. Thermal resistance = ΔT / power. Table 2 shows the measurement results obtained with power = 5 W. In Comparative Example 1, a sufficient sheet could not be obtained as described above, and therefore, all of the following evaluations including this evaluation could not be performed.

(Evaluation-2: Measurement of thermal conductivity)
Moreover, the thermal conductivity (W / m · K) was obtained from the following equation using the measurement results. Thermal conductivity = (power × T) / (S × ΔT). Here, power = 5 W, T is the thickness (50 μm: 5 × 10 ⁻⁵ m) of the thermal conductive sheet, and S is the area (m ² ) of the thermal conductive sheet. The measurement results are shown in Table 2.

(Evaluation-3: Evaluation of fluidity (wetting property) of the surface of the heat conductive sheet)
After heating the thermal conductive sheets prepared in Examples 1 to 6 and Comparative Examples 2 to 5 to a temperature of 80 ° C., the release film on the surface was peeled off, and the surface of the thermal conductive sheet was traced with a finger to obtain a surface state. Was evaluated by tactile sensation. The surface of the heat conductive sheet was fluidized, there was a sticky feeling, and wetting of the surface could be confirmed: ○, the surface of the heat conductive sheet was not fluidized and not wet: x was evaluated based on the judgment criteria. The results are shown in Table 2.

(Evaluation of recyclability)
(Evaluation-1: Evaluation of adhesive strength of thermal conductive sheet at a temperature of 23 ° C.)
Regarding the recyclability, the adhesive strength of the thermally conductive sheet at room temperature (for example, temperature 23 ° C.) was evaluated. First, the heat conductive sheet was cut into a size of 25 mm wide × 15 cm long, and the release film was peeled off and attached to a stainless steel plate. Next, the prepared sample was warmed to a temperature of 80 ° C. and left at a temperature of 80 ° C. for 10 minutes. Then, it returned to room temperature, peeled the said heat conductive sheet from the stainless steel plate at 180 degrees, and measured the peeling strength in that case. The measurement results are shown in Table 2.

(Evaluation-2: Evaluation of adhesive residue)
After the peel strength measurement in Evaluation-1, the amount of the thermally conductive composition 100 remaining on the surface of the stainless steel plate was visually observed. On the appearance, there was no adhesive residue: ○, on the appearance, the adhesive residue was apparent: x, Was evaluated. The evaluation results are shown in Table 2.

(Measurement of storage modulus)
The ratio of the storage elastic modulus at a temperature of 23 ° C. and 80 ° C. (storage elastic modulus at 23 ° C. ÷ storage elastic modulus at 80 ° C.) was measured using the prepared heat conductive sheet. For the measurement, a rotational / vibration type rheometer manufactured by Rheology is used to measure the storage elastic modulus at each temperature of 23 ° C. and 80 ° C., and the ratio of the storage elastic modulus is “storage elastic modulus at 23 ° C. ÷ It was calculated | required from 80 degreeC storage elastic modulus. The results are shown in Table 2.

  From the evaluation results shown in Table 2, Examples 1 to 6 of the present invention have low values of thermal resistance and high thermal conductivity, and have sufficient suitability as a thermal conductive sheet, and are also related to recyclability. Was also found to be excellent. Further, the thermal conductive sheets listed in Comparative Examples 2 to 5 are all unsuitable as thermal conductive sheets because of their high thermal resistance values and low thermal conductivity. In particular, Comparative Example 5 was found to have high adhesive strength at room temperature, poor adhesive residue, and poor recyclability.

It is a figure which shows one Embodiment of the heat conductive composition which concerns on this invention. It is a figure which shows one Embodiment of the heat conductive sheet which concerns on this invention. It is a figure which shows one Embodiment of the usage method of the heat conductive composition which concerns on this invention.

Explanation of symbols

  1: mixed polymer, 2: thermally conductive filler, 3: base film, 4: CPU, 5: heat sink, 100: thermally conductive composition, 200: thermally conductive sheet

Claims (10)

50 to 95 parts by weight of a first side chain crystallizable polymer that softens at an exothermic temperature of the heating element, and is incompatible with the first side chain crystallizable polymer and exhibits fluidity at the exothermic temperature of the heating element. Containing 50-5 parts by weight of a two-side chain crystallizable polymer;
A heat comprising 10 to 300 parts by weight of a heat conductive filler with respect to 100 parts by weight of a solid content of the mixed polymer of the first side chain crystallizable polymer and the second side chain crystallizable polymer. Conductive composition.   The melting point of the first side chain crystallizable polymer and the second side chain crystallizable polymer are both 30 ° C. or higher and crystallizes at a temperature lower than the melting point. Thermally conductive composition. 30 to 100 parts by weight of acrylic acid ester or methacrylic acid ester each having a linear alkyl group having 16 or more carbon atoms in both the first side chain crystallizable polymer and the second side chain crystallizable polymer;
70 to 0 parts by weight of an acrylic acid ester or methacrylic acid ester having 1 to 12 carbon atoms,
The heat conductive composition according to claim 1 or 2, which is a polymer obtained by polymerizing 0 to 10 parts by weight of a polar monomer.   4. The heat conductive composition according to claim 1, wherein the first side chain crystallizable polymer has a weight average molecular weight of 10,000 to 300,000. 5.   4. The heat conductive composition according to claim 1, wherein the second side chain crystallizable polymer has a weight average molecular weight of 1000 to 10,000. 5.   The ratio of storage elastic modulus at a temperature of 23 ° C. and 80 ° C. of the heat conductive composition (storage elastic modulus at 23 ° C. ÷ storage elastic modulus at 80 ° C.) is 100 or more. Item 6. The heat conductive composition according to any one of Items 5 to 6.   The heat conductive composition according to any one of claims 1 to 6, wherein an adhesive force of the heat conductive composition at a temperature of 23 ° C is 50 g / 25 mm or less.   The form of the said heat conductive composition of the said Claim 1 is a sheet form, The heat conductive sheet characterized by the above-mentioned.   The heat conductive sheet according to claim 8, wherein the sheet has a thickness of 20 µm to 200 µm. The heat conductive sheet according to claim 1, wherein the heat conductive composition is provided on both surfaces of a base film having heat conductivity.

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